1. Field of the Invention
The present invention relates to a display device mounted on a portable terminal. More particularly, the present invention relates to a lighting device which facilitates reduction in the thickness of a backlighting device and a display device including the lighting device.
2. Description of the Related Art
Generally, the term “display device” refers to a device for presenting a screen with a provided image signal. The display device has been widely used in daily life for not only portable terminals, such as cellular phones, Portable Multimedia Players (PMPs), etc., but also electric appliances, such as navigation systems for vehicles, televisions (TVs), laundry machines, refrigerators, etc.
With the common use of a flat-panel display device such as a Liquid Crystal Display (LCD), the display device can now be mounted on a small-size device such as a portable terminal. Recently, a combination of a touch screen panel and a display device implements a virtual keypad on a screen in place of a physical keypad of the portable terminal.
Since the flat-panel display device cannot emit light itself, the display device visually presents a screen implemented through the display device with light provided from a separately installed light source. The flat-panel display device, at its early stages of development, displayed a simple character or symbol with combinations of black and white, such that lighting can be sufficiently provided by installing a point light source at a side of the display device.
Recently, however, as a television or a monitor for a computer, which uses a flat-panel display device, has been popularized and a multimedia service using a portable terminal is also rapidly increasing, there is a limitation in providing lighting for the flat-panel type display device with a point light source which has a large deviation in backlighting according to an installation position. As a result, effort has been exerted to provide lighting uniformly over the entire area of the display device by using a light guide plate or a sheet diffuser which converts a point light source into a surface light source. In addition, a reflection plate for efficient use of light generated from the light source is also mounted in the flat-panel type display device.
FIG. 1 is an exploded perspective view of a display device according to the related art. The display device 10 implements an image based on a provided image signal through a flat-panel display device 21, and a backlighting device including a light source (not shown) provides lighting to allow a user to view the image implemented through the flat-panel display device 21. The backlighting device includes a light guide plate 12, a sheet diffuser 13, and a prism sheet 14 which are disposed on a frame 11, and the light source (not shown) is disposed on at least a side of the light guide plate 12. A plurality of light sources may be installed in an actual product according to a size of the flat-panel display device 21 or the like.
The frame 11 may be provided to enclose a back surface and side surfaces of the flat-panel display device 21 while maintaining the shapes of the light guide plate 12, the sheet diffuser 13, and the prism sheet 14.
The light guide plate 12 allows the light provided from the light source to be radiated over the entire area of the flat-panel display device 21. In other words, a line light source radiated from the light source is converted into a surface light source through the light guide plate 12.
The sheet diffuser 13 uniformly adjusts the light radiated from the light guide plate 12 toward the flat-panel display device 21 over the entire area of the flat-panel display device 21. The light passing through the sheet diffuser 13 is refracted in various directions, thereby passing through the prism sheet 14.
The prism sheet 14 converts side light, which passes through the sheet diffuser 13 and then goes in an inclined direction with respect to the flat-panel display device 21, into front light. That is, the light passing through the prism sheet 14 enters the prism sheet 14 perpendicular to a surface of the flat-panel display device 21.
The backlighting device described above is adhered to a back surface of the flat-panel display device 21 through a separate adhesive sheet (not shown).
The light radiated from the light guide plate 12 also goes to a back surface which does not face the flat-panel display device 21, degrading lighting efficiency. Therefore, the backlighting device preferably includes a reflection plate 15 on the back surface of the light guide plate 12.
The reflection plate 15 forms a reflection layer by depositing a metal component such as aluminum on a surface of a deposition film. In this case, since it is difficult to secure a sufficient refractive index only with a general metal component, deposition films on which reflection layers are formed are laminated and thermally compressed, after which thickness is reduced by a stretching process and a surface area is expanded, thus completing the reflection plate 15. The completed reflection plate 15 is adhered to the back surface of the light guide plate 12 or the frame 11 through a separate adhesive tape 16.
However, in the backlighting device of the related art, the reflection plate has disadvantages of a complex manufacturing process and a high possibility of a crack being generated in the reflection layer or the deposition film. Moreover, the reflection plate is manufactured by laminating the plurality of deposition films and then performing the stretching process, such that to dispose the reflection plate in an actual product, a separate cutting process and an adhering process using an adhesive tape are required. As a result, the assembly process of the reflection plate to the backlighting device as well as the manufacturing process of the reflection plate is cumbersome. Moreover, the thickness of the adhesive tape as well as the thickness of the reflection plate including the deposition films hinders reducing the thickness of the display device.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as Prior Art with regard to the present invention.